What is Electrostatic force: Definition and 184 Discussions

Coulomb's law, or Coulomb's inverse-square law, is an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles. The electric force between charged bodies at rest is conventionally called electrostatic force or Coulomb force. The law was first discovered in 1785 by French physicist Charles-Augustin de Coulomb, hence the name. Coulomb's law was essential to the development of the theory of electromagnetism, maybe even its starting point, as it made it possible to discuss the quantity of electric charge in a meaningful way.The law states that the magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them,















{\displaystyle |F|=k_{\text{e}}{\frac {|q_{1}q_{2}|}{r^{2}}}}
Here, ke is Coulomb's constant (ke ≈ 8.988×109 N⋅m2⋅C−2), q1 and q2 are the signed magnitudes of the charges, and the scalar r is the distance between the charges.
The force is along the straight line joining the two charges. If the charges have the same sign, the electrostatic force between them is repulsive; if they have different signs, the force between them is attractive.
Being an inverse-square law, the law is analogous to Isaac Newton's inverse-square law of universal gravitation, but gravitational forces are always attractive, while electrostatic forces can be attractive or repulsive. Coulomb's law can be used to derive Gauss's law, and vice versa. In the case of a single stationary point charge, the two laws are equivalent, expressing the same physical law in different ways. The law has been tested extensively, and observations have upheld the law on the scale from 10−16 m to 108 m.

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  1. mangofan

    I Electrostatic force exerted on an electron inside a nucleus

    This is SAMPLE PROBLEM 25-7 from "Physics" by Resnik, Halliday, and Krane, in the chapter "Electric Field and Coulomb's Law". After describing the behavior of uniformly charged spherical shells: follows a sample problem: The solution to (a) goes to say that the volume inside R/2 is 1/8 of the...
  2. T

    A Is Gravity Just the Electrostatic Force?

    I read this paper and this is iindeed a very interesting hypothesis. The implications of this theory if true are enormous! Please comment! Is Gravity Just the Electrostatic Force? <crackpot link deleted>
  3. M

    Help with Coulomb's law: Net electrostatic force

    I tried just calculating the force with Coulomb's law, then calculating the forces for each vector individually and adding, but I got it wrong both ways
  4. B

    I How to ensure an equation is dimensionless when it includes "Debye"

    I am trying to check if an expression is dimensionless. If it is, then I have done things correctly. However, I am stuck on how to deal with a (Debye^2) term. How can I break it down to find out if it cancels out with the other units I have left? I know this is probably a trivial question...
  5. E

    Does the electrostatic force create current in the circuit?

    As I understand potential difference is the reason of current. Does it mean that the electrostatic force creates current?
  6. Prabs3257

    Electrostatic force equilibrium

    I was thinking that we can equate the electrostatic potential energy and the spring energy (as the force is similar to that of a spring so energy will also be 1/2kx^2 ) but i am not getting the correct ans but by equating the net force on one charge to kr i am getting the correct ans can...
  7. T

    Electrons cannot sense electrostatic force?

    Why there is not voltage or current just for 1ms if I connect a multimeter ground to the negative terminal of a DC power supply or charged capacitor? Why electrons in measure lead and DMM device cannot sense a bulk of electrons (or lack of it)? I tried with an 5kV DC power supply too. In an...
  8. Salman Ali

    How do the charges in 3 cancel each other out in net electrostatic force?

    Here is the question no1 in image. A charge is in between . We will let it possitive or negative. The answer is 3,1,2 4...But how? Won't the charges in 3 cancel each other out because they are possitive at right and negative at left. One is attracting so the other is repelling.
  9. iVenky

    Electrostatic force with and without a conductor in between

    The figure shows a charge q1 exerting a force on a test charge qu. What happens to the electric force when a conductor is placed between q1 and qu (cases 1 and 2)? Does the force still remains the same? I am asking this because I am actually interested in finding what happens to the flux in...
  10. P

    How many electrons were transferred to create an attractive force of 1 N?

    So there was a question in a textbook that went as so: 'Two point charges (30 cm apart in air) are charged by transferring electrons from one point to another. Calculate how many electrons must be transferred so that an attractive force of 1 N exists.' It is assumed that both point charges...
  11. S

    Confusion about the Lorentz force

    We can find the force by finding the E-field on the charge first, then applying Lorentz force formula. However, it isn't obvious to me at all how to find the E-field. If the charge were on top of the hemisphere I would be using spherical coordinates, but here I don't know which coordinate system...
  12. psy

    Electrostatic Force and Field between two charges

    Two positive point charges with a charge of 10nC each are 10cm apart. What is the electric field strength at point A? How is it directed? Which force acts on a charge of 100nC at point A? F = k * q1 * q2 / r^2 E = F/q r^2 = (l1/2)^2 + (l2)^2 => r = 0,707m Electric field strength : E1 = E2 =...
  13. T

    Electrostatic force between a Half Cylinder and a Plate

    Homework Statement (This is not a HW problem, but HW-type problem.) A half cylinder of radius R and length L>>R is formed by cutting a cylindrical pipe made of an insulating material along a plane containing its axis. The rectangular base of the half cylinder is closed by a dielectric plate of...
  14. Fraser MacDonald

    What is the electrostatic force field?

    I have just covered the electricity unit in my advanced higher physics course, and have happily accepted that a force is created between charged particles. I understand that coulombs law can be used to calculate this force, but here is my question. What actually is this force between the charged...
  15. S

    Electrostatic Force - Locations of a second charge

    Homework Statement A force of 2.4N [L] is exerted on a -1.8x10-6C charge 0.2m away. What are the possible charges and locations of the second charge? Homework Equations FE= kq1q2 / d2 The Attempt at a Solution Rearranging the equation above for q2 is q2 = FE x d2 / kq1 and substituting...
  16. R

    What is the net electrostatic force of the sphere at the origin?

    Homework Statement Three charged metal spheres are arrayed in the xy plane so that they form an eqilateral triangle. What is the net electrostatic force on the sphere at the origin? http://imgur.com/a/4XnoO (sorry I forgot to put this but the angles are 90 for each vertex, which should be...
  17. S

    Potential Difference & Force on Electrostatic Sphere

    Homework Statement A uniformly charged, solid, non-conducting sphere of radius ##a## and charge density ##\rho## has its center located a distance ##d## from a uniformly charged, non-conducting, infinite sheet (charge density ##\sigma##). Determine the potential difference between the center of...
  18. Vishakha

    Maximizing Electrostatic Force between Two Point Charges

    Homework Statement Two point charges q and λq located at the points, x=a & x=μa respectively. If the sum of the two charges is constant,what is the value of λ for which the magnitude of the electrostatic force is maximum?Homework Equations The Attempt at a Solution For force to be maximum dF/dq...
  19. L

    Electrostatic Force: +3.2 C & -1.6 C Magnitude of Force

    Homework Statement I have a question that I think I know, but it is kind of confusing me a little bit. The problem is as following: Consider a charge of +3.2 C and a charge of -1.6 C separated by a distance of radius r. Which of the following statements correctly describes the magnitude of...
  20. J

    Calculating electrostatic force on particles

    Homework Statement Homework Equations F=(kq1q2)/d^2 The Attempt at a Solution So it should be fairly easy to use "parts" to come up with each answer Part a Because particle 1 has no pull in the x direction I should be able to ignore it when finding the x component of the force...
  21. Funner

    Electrostatic force on polymer particle in an electric field

    Hi there, in electrospinning, a positive charge of around 10.000Volt is applied to a needle, where a viscous polymer is extruded. There is a grounded collector in a distance of 15mm and the established electrical field generates electrostatic forces and draws a thin polymer jet to the...
  22. S

    What is the *truth* of the electrostatic force

    Hey guys, I want to ask a question about the Coulomb force or the electrostatic force. As you can see, there are these statement, 1) The electric force is a "vector quantity" 2) The electric force between two stationary charged objects is called the Electrostatic force. 3) The electrostatic...
  23. Aldo Biko

    The force between charged and neutral object

    Homework Statement I did a lab involving Van de Graaff generator. Basically, below the charged sphere, I put a neutral sphere on a scale and measure the difference in mass which then I can calculate the force acting on the neutral sphere. I repeated the experiment with different distance. What...
  24. J

    Missmatch in electrostatic force calc. by different methods

    I have been looking into the forces exerted by electrostatic fields and have come up with different answers using two different methods. I would appreciate any help in pointing to a reference that will reconcile this or point to an error in my methods. To keep things simple I am using a one...
  25. Y

    Force on a charge due to charged sheet

    Homework Statement I want to find the force on a positive charge placed at a distance ##d## from a positively charged infinite plate. Of course, it can be simply done by finding the electric field due to the plate using Gauss's Law. But my teacher suggested a different method and I am unable...
  26. UchihaClan13

    What is the explanation for the electrostatic force between two charged bodies?

    Okay guys It's no wonder I love electrostatics I keep on getting so many doubts Okay my doubt goes like this Consider 2 charges(q1and q2 having masses m1and m2 (here i am assuming that these two aren't point charges and therefore don't have negligible volume/mass) Okay so i am neglecting the...
  27. Monkey_Man08

    What is the unknown charge if the net electrostatic force on particle 1 is zero?

    1. The problem statement: In the figure four particles form a square with edge length a = 2.44 × 10-2 m. The charges are q1 = q4 = 1.06 × 10-15 C and q2 = q3 = q. What is q if the net electrostatic force on particle 1 is zero? All variables and given/known data: The given variable are in the...
  28. E

    Electrostatic force between two halves of sphere

    Homework Statement Find the electrostatic force of interaction between two halves of a spherical conductor of radius R carrying a charge Q. This thread already exists- https://www.physicsforums.com/threads/electric-force-between-two-halves-of-a-sphere.317380/ but is closed. Homework Equations...
  29. C

    How to get maximum electrostatic force?

    Homework Statement Let's take two spheres that are somewhat nearby. On one sphere, sphere A, there is Q units of charge. Now, we take some little bit of charge q off of sphere A, and put it on sphere B. What should the ratio q/Q be if we want the electrostatic force between the spheres to be a...
  30. T

    Finding magnitude of electrostatic force

    We have a question about finding the electrostatic force acting on a particle from another particle. They are colinear since there is only the 2 particles, but not along an axis. My question is, why does finding the force in the x direction and finding the force in the why direction, then...
  31. W

    I'm making an Arithmetic Error, Electrostatic force diagrams

    Homework Statement Three charged particles are placed at each of three corners of an equilateral triangle whose sides are of length 2.7 cm . Two of the particles have a negative charge: q1 = -6.0 nC and q2 = -12.0 nC. The remaining particle has a positive charge, q3= 8.0 nC . What is the net...
  32. G

    Finding magnitude of electrostatic force

    Homework Statement Im having trouble posting the image sorry. But there's three charges. q1=30uC q2=? q3=60uC q1 to q2 distance equals 30cm q2 to q3 distance equals 60cm q1 is left of q2 and q3 is to the right of q2. Homework Equations F=k*qq/r^2 The Attempt at a Solution [/B] Given where q2...
  33. P

    Electrostatic and gravitational force

    Homework Statement Point charge Q = 4.26 μC is fixed at the origin. Now, point charge q = 4.88 μC is carefully placed directly above it (along the y-axis), and it floats at (0,9.51 cm). Find the mass of q, in kg. Assume: g = 9.803 m/s^2. Homework Equations F=kq1q2/r^2 G=mg probably The...
  34. J

    When current flows through 2 parallel wires (same amount of current)

    when current flows through 2 parallel wires (same amount of current); the protons in the first wire would see the electrons drifting in a direction and also in the other wire (in the same direction). They would appear to be contracted in the direction which they flow due to length contraction...
  35. J

    Electrostatic Force Between Proton and Neutron?

    After calculating the force upon an electron and a force upon a proton in the atom of hydrogen, my result was a force of ≈8.2x10-8 Newtons acting upon the electron and proton each. If found this by using the formula Fe = (ke q1q2)/r2 Taking this number, I then applied it in the formula F = ma...
  36. W

    Electrostatic Force Concept Question

    Homework Statement Consider an electron-proton pair and compare its electrostatic force with that of the gravitational force [G=6.67x10^11 Nm^2/kg^2]. Homework Equations F = k * |q1 * q2| / r^2 k = 1/4π∈ The Attempt at a Solution I calculated the force by using the charge of an electron...
  37. Emily_20

    Calculating Electrostatic Force Between Pennies with Slight Charge Differences

    Homework Statement We know that the magnitudes of the negative charge on the electron and the positive charge on the proton are equal. Suppose, however, that these magnitudes differed from each other by as little as 0.0001%. With what force would two copper pennies, placed 1.0 m apart, repel...
  38. S

    Why does electrostatic force move water but not magnetism?

    So I was surprised to notice that my plastic shopping bag was able to actually push and pull tap water significantly far with its electrostatic force. But when I put a magnet near the water nothing happened. What makes the electrostatic force so different from magnetic force; isn't it just two...
  39. L

    What is the electrostatic force on the Y charge?

    First off idk if this is the right topic to post in but I've been at this problem for hours and I have no idea how to solve it. Three metal spheres are situated in positions forming and equlateral triangle with sides of 0.012 m. X has a charge of -2.5 C. Y has a charge of 3.00 C. Z has a charge...
  40. arpon

    Problem on electrostatic force

    Homework Statement A metal sphere of radius R and total charge Q is cut into two equal halves. Find the force that is necessary to hold the two parts together. Homework Equations ##F = \frac{1}{4\pi \epsilon _0} \cdot \frac {q_1 q_2}{r^2}## ##\oint \vec E \cdot d \vec A = \frac{q}{\epsilon...
  41. M

    Hai Calculating Net Electrostatic Force Need help :(

    Homework Statement Three charged objects are placed as shown. Find the net force on the object with the charge of -5uC Diagram:[/B] http://imgur.com/xHGHGbd Homework Equations No idea what to do as far as steps go, I don't know how to start :([/B]The Attempt at a Solution None so far.
  42. PhysicoRaj

    Electrostatic force in a medium of non uniform permittivity

    Homework Statement Two point charges, +4 μC and -10 μC are placed 10 cm apart in air. A dielectric slab of large area and thickness 5 cm is placed between the charges. Find the force of attraction between the charges, if the dielectric has a dielectric constant of 9. Homework Equations...
  43. E

    What factors could alter electrostatic force?

    While investigating Coulomb's Law, I created a graph of F-1/2 vs. r to display results. The gradient of this graph is much steeper than it should be. What factors could affect the electrostatic force to make this happen? Any suggestions would be greatly appreciated! (The experiment...
  44. D

    MHB Electrostatic Force: Effects of Distance

    How does electrostatic force vary between two objects if the distance is doubled? I know with gravitational force as the distance doubles the force decreases by \(\frac{1}{4}\).
  45. D

    Electrostatic force, voltage, electrostatic potential

    Hello everyone I am stuck with a problem about voltages (electrostatic potential) and forces. According to capacitor equations the energy stored in the capacitor is: U=1/2*C*V^2 And force is: F = - dU/dx Since U is dependent on V^2, our force can’t be positive (repelling...
  46. M

    Electrostatic force between 2 hemispheres

    Homework Statement A metal sphere of radius R carries a total charge Q, what is the force of repulsion between the northern and southern hemispheres Homework Equations \large f=\sigma Eav=1/2 \sigma(Eabove+Ebelow). \\Fz=\int fz dA =\int \sigma Eav cos\theta R^{2}sin\theta d\theta d\phi=\int...
  47. N

    Finding the magnitude of the electrostatic force from a thin rod

    Homework Statement The figure shows a uniformly charged thin rod of length L that has total charge Q. Find an expression for the magnitude of the electrostatic force acting on an electron positioned on the axis of the rod at a distance d from the midpoint of the rod...
  48. X

    Work done by electrostatic force. Positive or negative?

    Homework Statement A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force: a) does positive work and increases the kinetic energy of the small sphere b) does negative work and...
  49. S

    Does the Electrostatic Force Originate from Curvature? An Explanation

    einstein explained the origin of gravitational force from the concept of space time curvature.but what about the electrostatic force...does it also originate from some sort of curvature.please explain...
  50. X

    Work done by electrostatic force

    Homework Statement A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force: a) does positive work and increases the kinetic energy of the small sphere b) does negative work and...